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Drilling holes in pipe in a perpendicular line.

Hello. This is my first post here, and I'm not even what you would call a amateur yet, so bear with me.

I need to drill a series of holes in some pipe... but I need the holes to line up from one end to the other, in other words, when I put bolts through the holes, I need them to all line up in a plane... not like a spiral staircase.

Seems simple enough.

I bought a halfway decent drill press and a drill press vice, and set it up so the holes would be centered in the pipe... then I created a jig from some angle iron, so I could put a bolt through the first hole, and the jig would show me where the next hole needed to go. I figured with the vice holding the pipe, I would get what I wanted.

Well, I almost got it. When I was done, I looked down the pipe, and the "top" side of the pipe, all the bolt heads were in a nice line... however, the bottom ends are off randomly in different directions, so it ain't going to work.

Studying the problem, it seems like the jig is able to flip flop on the top of the pipe as I'm drilling... pulling the drill bit slightly off to one side of the other.

This weekend, I'm going to attempt this again. I am going to pick up a V shaped pipe drilling jig, and I'm going to make a new 'hole distance' jig out of thicker steel and clamp it to the press table under the V shaped pipe drilling jig. By bolting a bolt into the 'hole distance' jig, I hope that I will get a perpendicular line of holes drilled in the pipe.

Does this sound like it should work, or is there a particular technique for attempting this? Thanks in advance.

If you use a center drill to spot the hole before drilling, you should be able to avoid your hole "walking" on you. Pics of your jig would be helpful to see if there is anything noticeably wrong with it. Otherwise it's all conjecture. Ask 3 different people to imagine something with a small description and all 3 will have different imaginings of what that something is.

If you use a center drill to spot the hole before drilling, you should be able to avoid your hole "walking" on you. Pics of your jig would be helpful to see if there is anything noticeably wrong with it. Otherwise it's all conjecture. Ask 3 different people to imagine something with a small description and all 3 will have different imaginings of what that something is.

Too true! Post a pic or two.
That said, maybe you could drop a bolt through the first hole you drilled, centerdrill one side of the tubing in the second hole's location, flip the tube, and centerdrill and drill the hole through from the second side. The centerdrill's small hole will locate the drill and keep it from walking inside the tube, and the bolt through the first hole will clock the rest of the holes with the first.

Holes through pipes

Dear BKNJ,

First of all, welcome.

I have been through a similar drilling problem recently. You have a great accuracy on the entry holes on the top surface of the pipe as you go in. Yes, use a centre drill on the jig, and the top holes are just fine.

But think what happens when the drill bit starts to try to go through the other side of the pipe. It is trying to centre on a concave surface, and may well skate all over the place if it is not really rigid.

My best guess is to drill entry and exit holes from top and bottom in two operations. If you have some kind of V block jig to clamp the pipe on your drill press, you just stick a marker on the pipe to indicate its position radially, and then rotate the pipe through 180 degrees to drill the exit hole from the other side of the pipe, from the outside.

martinW...by the very nature of a concave surface, this should aid in elimination of drill bit wandering...after all, what is the depression left by a ball mill if not concave? Anytime I have to drill an offset hole in a surface that is round or flat, I spot the location with a suitable ball mill to prevent my drill bit from walking...works a miracle, every time.

307startup and vlmarshall... yeah, photos would be nice, but unfortunately, the setup is at my weekend (true) home... 130 miles from my weekday home, and photos were not a option at the time. As far as trying to clarify the setup a bit more... the vise is one of these...

The pipe is clamped so that the hole will be centered... the angle iron jig with two holes is laid on top, a bolt locating the jig to the pipe's first hole... I then drill the next hole using the jig as a guide. Its clearly not the most professional setup... but I expected the jig to only act as a distance guide... I thought the vise would ensure the holes drilled would be centered on both sides.

That said, I have to agree with 307 that I would think the concave surface would help locate the center of the pipe, but I could be obvious wrong. I also not that I am somewhat disappointed in how much deflection I see with the drill bits... I never noticed this inaccuracy before, and I wonder if this is from cheap drill bits (they certainly didn't have a cheap price!) or is a potential weakness in the drill press I bought. I fear that somethings are just made to be quality anymore.

Nonetheless, I like the ideas posted to drill the holes topside and flip the pipe and drill the bottom side. I never would have thought of such a simple idea. I'm still going to pick up a V block fixture, as Harbor Freight sells one for cheap... assuming that I can get that properly setup, it should make things easier (I was SO tired of opening and closing the vise last weekend... I had to do about 200 holes in other pipes and it got old setting up and resetting up the thing!).

How about clamping a rectangular block (wood?) to the end of the pipe to give you a 0/180 degree reference and extending the drilling table with something flat (i.e. a table? or a length of plate) to give the block something to sit on.

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If you want the holes true, you really need to drill in from each side - it's a pain, but there's no way to be sure if the drill is going in the right place if it's inside the pipe.

The more time you spend getting the jig right, the faster and more accurate the finished job.

I considered bolting it down to a length of wood, but I figured I would have a hard time getting two holes perpendicular just under 8 ft apart. I also figured that I could locate the first hole, but attempting to locate the second hole in the other end would result in an extra hole, since the incremental error in each jig drilled hole would likely add up, and move the final hole +/- 1/4". I also considered sandwiching the pipe between two pieces of wood, with predrilled guide holes... but without a miter bit and a table saw, I figured making a half circle grove in both boards would be too much trouble.

As for a seam, the pipe does have a seam, but its pretty thin, like the rest of the pipe. I'll check to see if I lined up my holes opposite the seam and if that threw off things.

Just in case any one was wondering, I am building a solar panel array that will move in two axises to follow the sun. The pipes I am drilling are for the actual 8' x 8' movable frame the solar panels will mount to. Unfortunately, the cheapie solar panels I bought have little accommodations for mounting and a thin frame border, so I need to clamp them down to the frame... this is why I need the bolt holes to be reasonable straight and lined up.

In the future, I will be likely building my own solar panels from smaller solar cells sandwiched between transparent lexan of some sort... which will be easier to mount and hopefully cheaper per watt... <$2 a watt versus the prebuilt $5 a watt panels.

Clamp the pipe onto a flat surface (e.g. a sheet of MDF/Ply) then move the drill along the pipe (have you a small bench top drill or a press adapter for a hand drill, that you can rotate the head clear of the base?)

You could use a stubby bit (or snap off and re-grind a longer one) and drill straight through, as the critical hole is only in one side.

If this is seamed tubing, is it possible you are blindly hitting the seam sometimes?

Dear Neil,

That was just brilliant. I completely missed that potential problem and will bear it in mind when I try something similar. I will however still drill from both sides because I do not have spiffing machine tools. ...wish I had...